This invention relates generally to box handling apparatus, and more particularly to box handling apparatus for semiconductor wafer packaging.
The final stages of semiconductor wafer production are conventionally carried out in a clean room so that the finished wafers are free from particulate matter deposits and moisture. The condition of the wafers must be maintained as they are transported to a facility in another city or country. Moreover, the wafers must not be physically damaged either by the packaging process or by the rigors of their transportation.
Accordingly, specialized transportation boxes have been developed for transportation of the semiconductor wafers. Typically, these boxes contain a cassette which holds multiple wafers with minimal contact of the front and rear surfaces of the wafer. The cassette is formed with integral dividers defining slots, each of which receive a wafer. The wafers may be loaded into the cassette slots manually, or automatically by presently available machinery. The loaded cassettes are manually placed in a bottom of the box. A lid of the box is placed on the bottom over the cassette and pressed down against the bottom. The box is designed for a snap-latching interengagement of the lid with the bottom. To insure that the lid and bottom are sealed together, tape may be applied around the circumference of the box over the joint between the lid and bottom. The box is then sealed inside a flexible, moisture barrier package (e.g., an aluminum coated acrylar polymer material).
Conventionally, a technician manually opens the box, places the cassette into the box and then manually closes the box. In practice several boxes would be opened at one time so that cassettes could be loaded substantially continuously. The chance of contamination of the wafers in the cassette from particulates and/or moisture is greatly increased when the cassette is handled manually. Moreover, as the box lays open for a period of time there is also an increased opportunity for particulates and moisture to enter the box. Particulates on the interior of the box can readily become deposited on the wafers after the box is closed.
To close the box after the loaded cassette is placed in the bottom portion, a technician presses down on the lid of the box. It is difficult for the technician to apply equal pressure around the box in order to make sure that the lid and bottom portion are latched together. Moreover, failure to apply equal pressure on the lid can cause the wafers in the cassette become "cross slotted". The box is designed so that wafers held in the slots of the cassette are received in aligned slots of the lid. Cross slotting occurs when a wafer held in one slot of the cassette enters a non-aligned slot in the lid when the box is closed. Cross slotting can damage the wafer and generate particulate matter which may become deposited on other wafers in the box.
Thus, there is presently a need for apparatus and a method to handle boxes which is particularly useful in the packaging of semiconductor wafers to protect the wafers from damage and contamination by moisture or particulates.